Paper feeding apparatus with paper size detectors

ABSTRACT

A paper feeding apparatus includes a cassette main body that stacks a paper therein, a sidewall that moves in a width direction of the cassette main body, an end wall that moves in a longitudinal direction of the cassette main body, a first movable member that is connected at one end to the sidewall and rotates around a shaft axially fixed to the cassette main body in connection with the sidewall, a second movable member that is connected at one end to the end wall and rotates around a shaft axially fixed to the cassette main body in connection with the end wall, a first detection unit that has a plurality of detection members and detects the size of the paper in the width direction, and a second detection unit that has a plurality of detection members and detects the size of the paper in the longitudinal direction.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/765,632, filed Apr. 22, 2010, which is a continuation of U.S. patentapplication Ser. No. 12/207,468, filed Sep. 9, 2008, now U.S. Pat. No.7,731,183, issued Jun. 8, 2010. This application claims the benefit ofU.S. Provisional Applications No. 60/971,237, filed Sep. 10, 2007; No.60/971,238, filed Sep. 10, 2007; No. 60/971,246, filed Sep. 10, 2007;No. 60/972,237, filed Sep. 13, 2007; No. 60/988,733, filed Nov. 16,2007; and No. 60/988,751, filed Nov. 16, 2007. Each of theseapplications is herein incorporated by reference.

TECHNICAL FIELD

The present invention relates a paper feeding apparatus that is capableof detecting the size of a paper stacked in a paper cassette.

BACKGROUND

In the related art, an image forming apparatus or a paper feedingapparatus is provided with a mechanism for detecting the size of a paperstacked in a paper cassette. With the enhancement of functionality ofthe image forming apparatus, the image forming apparatus becomescomplicated and has a lot of members. In terms of user's convenience, itis undesirable that the image forming apparatus is increased in heightin a height direction. Therefore, it is necessary to reduce the heightof the paper cassette in the paper feeding apparatus disposed at a lowerend of the image forming apparatus.

With the enhancement of functionality of the image forming apparatus, inorder to suppress an error when printing, it is necessary to accuratelydetect the size of the paper stacked in the paper cassette.

The paper cassette has a sidewall and an end wall that are movable alonga width direction of the stacked paper and a longitudinal direction ofthe paper cassette. Two paper size sensors for detecting the size of thepaper stacked in the paper cassette when the paper cassette is insertedinto the paper feeding apparatus are provided at a position opposed tothe paper cassette on the depth side of the paper feeding apparatus.Each of the paper size sensors detects the size in the paper widthdirection or the longitudinal direction of the paper cassette bycombinations of presses. A control unit detects the paper size on thebasis of a combination of the sizes in the paper width direction and thelongitudinal direction of the paper cassette detected by the two papersize sensors.

The paper cassette is provided with a movable member that is movable inaccordance with the movement of the sidewall, and a movable member thatis movable in accordance with the movement of the end wall. The movablemembers correspondingly press the paper size sensors. At this time, themovable member connected to the sidewall and the movable memberconnected to the end wall are disposed in the paper cassette with thesame rotation fulcrum.

FIGS. 47 and 48 show a related art example of a first movable member 205and a second movable member 206 provided in a cassette main body 201.FIG. 47 is a diagram of a paper cassette 201 when viewed from its rearsurface in a state where the paper cassette 201 is inserted into animage forming apparatus 1. FIG. 48 is a diagram of a first sensor 102and a second sensor 103 when viewed from the depth side of the imageforming apparatus 1.

As shown in FIG. 47, the first movable member 205 and the second movablemember 206 are disposed on the rear surface of the cassette main body201 on the same axis. Therefore, as shown in FIG. 48, the first sensor102 and the second sensor 103 are arranged in the height direction onthe same axis of the paper feeding apparatus 20 or the image formingapparatus 1. For this reason, the paper cassette 201 cannot be decreasedin height (JP-A-2005-280994).

When the printing position of an image is misaligned with respect to thepaper width direction, it is necessary to shift the paper position inthe paper cassette so as to be aligned with the image to be printed(hereinafter, referred to as lateral misalignment correction). When auser executes lateral misalignment correction of a paper, the sidewallis also moved. For this reason, the paper size sensors may detect a sizedifferent from a paper size desired to be actually detected or may notspecify any size. For this reason, when the user executes the lateralmisalignment correction of the paper in the paper cassette, it is alsonecessary to move the paper size sensors, which leads to complexity.

Instead of the lateral misalignment correction of the paper, a method ofcorrecting the position of an image when printing may be used. In thiscase, however, it is necessary to set a printable region in the imageforming apparatus by an amount corresponding to the amount of lateralmisalignment correction. For this reason, the image forming apparatus isincreased in size, and manufacturing costs become high. In addition,according to this method, the position of the paper in the papercassette is not corrected, and accordingly the paper is conveyed intothe apparatus at a position different from a normal position. Then, thepaper may collide against an unexpected place, and paper jam or bendingmay occur. When a lateral misalignment adjustment mechanism for thelateral misalignment correction is provided, it is necessary for theuser to adjust the paper size sensors.

Accordingly, aspects of the invention provide a paper feeding apparatusthat is capable of accurately detecting the size of a paper stacked in apaper cassette without increasing the size of the apparatus.

SUMMARY

According to one aspect of the present invention, there is provided apaper feeding apparatus comprising; a cassette main body that stacks apaper therein, a sidewall that moves in a width direction of thecassette main body, an end wall that moves in a longitudinal directionof the cassette main body, a first movable member that is connected atone end thereof to the sidewall, rotates around a shaft axially fixed tothe cassette main body in connection with the sidewall, and has a firstdetection portion at the other end thereof, a second movable member thatis connected at one end thereof to the end wall, rotates around a shaftaxially fixed to the cassette main body in connection with the end wall,and has a second detection portion at the other end thereof, a firstdetection unit that has a plurality of detection members and detects thesize of the paper in the width direction according to the firstdetection portion provided in the first movable member, and a seconddetection unit that has a plurality of detection members and detects thesize of the paper in the longitudinal direction according to the seconddetection portion provided in the second movable member.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the exterior of an image formingapparatus according to a first embodiment;

FIG. 2 is a block diagram showing a control system of a paper feedingapparatus according to the first embodiment;

FIG. 3 is a top perspective view of a paper cassette detachably mountedin the paper feeding apparatus according to the first embodiment;

FIG. 4 is a bottom perspective view of the paper cassette detachablemounted in the paper feeding apparatus according to the firstembodiment;

FIGS. 5A and 5B are diagrams showing the shapes of a first movablemember and a second movable member according to the first embodiment;

FIG. 6 is a top perspective view of the paper cassette detachablymounted in the paper feeding apparatus according to the firstembodiment;

FIG. 7 is a bottom perspective view of the paper cassette detachablymounted in the paper feeding apparatus according to the firstembodiment;

FIG. 8 is a diagram showing the rear surface of the paper cassetteinserted into the paper feeding apparatus according to the firstembodiment;

FIG. 9 is a diagram of a first sensor and a second sensor according tothe first embodiment when viewed from the depth side of the paperfeeding apparatus;

FIG. 10 is a diagram of the first sensor and the second sensor accordingto the first embodiment when viewed from the near side of the paperfeeding apparatus;

FIG. 11 is a diagram showing a sensor board according to a secondembodiment;

FIG. 12 is a diagram showing the structure of the sensor board accordingto the second embodiment;

FIG. 13 is a top view showing engagement of a first movable member and asecond movable member with the sensor board according to the secondembodiment;

FIG. 14 is a top view showing engagement of the first movable member andthe second movable member with the sensor board according to the secondembodiment;

FIG. 15 is a top view showing engagement of the first movable member andthe second movable member with the sensor board according to the secondembodiment;

FIG. 16 is a bottom view showing engagement of the first movable memberand the second movable member with the sensor board according to thesecond embodiment;

FIG. 17 is a flowchart showing detachment of the sensor board accordingto the second embodiment;

FIG. 18 is a diagram showing the structure of a sensor board accordingto a third embodiment;

FIG. 19 is a diagram showing the structure of the sensor board accordingto the third embodiment;

FIG. 20 is a diagram showing the structure of the sensor board accordingto the third embodiment;

FIG. 21 is a diagram showing the structure of a paper cassette to becoupled to the sensor board according to the third embodiment;

FIG. 22 is a diagram showing a state where the sensor board according tothe third embodiment and the paper cassette are coupled to each other;

FIG. 23 is a diagram showing a paper sensor provided at a front-sidesidewall according to a fourth embodiment;

FIG. 24 is a diagram showing the paper sensor provided at a rear-sidesidewall according to the fourth embodiment;

FIG. 25 is a diagram showing the paper sensor provided at an end wallaccording to the fourth embodiment;

FIG. 26 is a flowchart showing paper size detection by the paper sensoraccording to the fourth embodiment;

FIG. 27 is a top perspective view showing a part of a paper cassetteaccording to a fifth embodiment;

FIG. 28 is a diagram showing coupling of the rear-side sidewall and thefirst movable member according to the fifth embodiment;

FIG. 29 is a diagram showing coupling of the rear-side side wall and thefirst movable member according to the fifth embodiment;

FIG. 30 is a diagram showing the stretched state of a front-sidesidewall and the rear-side sidewall according to the fifth embodiment;

FIG. 31 is a diagram showing the retracted state of the front-sidesidewall and the rear-side sidewall according to the fifth embodiment;

FIG. 32 is a top perspective view showing the paper cassette accordingto the fifth embodiment;

FIG. 33 is a diagram showing a pinion gear mounted on the paper cassetteaccording to the fifth embodiment;

FIG. 34 is a diagram showing the pinion gear before being mounted on thepaper cassette according to the fifth embodiment;

FIG. 35 is a diagram showing the rear surface of a pinion gear holdingmember according to the fifth embodiment;

FIG. 36 is a sectional view showing the pinion gear according to thefifth embodiment;

FIG. 37 is a sectional view of the pinion gear according to the fifthembodiment;

FIG. 38 is a diagram showing the pinion gear holding member mounted onthe paper cassette according to the fifth embodiment;

FIG. 39 is a diagram showing the rear surface of the pinion gear holdingmember according to the fifth embodiment;

FIG. 40 is a diagram showing lateral misalignment correction of a paperby the pinion gear holding member according to the fifth embodiment;

FIG. 41 is a diagram showing the first movable member and a firstconnection member according to the fifth embodiment;

FIG. 42 is a diagram showing lateral misalignment correction of a paperby the first connection member according to the fifth embodiment;

FIG. 43 is a sectional view of the first connection member according tothe fifth embodiment;

FIG. 44 is a top view showing a paper cassette provided with a firstlink member according to a sixth embodiment;

FIG. 45 is a top view showing the paper cassette provided with a lateralmisalignment detection unit according to the sixth embodiment;

FIG. 46 is a diagram showing press of a first movable member 205 on afirst sensor 102 according to the sixth embodiment;

FIG. 47 is a diagram showing the rear surface of a paper cassetteinserted into a known paper feeding apparatus; and

FIG. 48 is a diagram of known first sensor and second sensor when viewedfrom the depth side of the image forming apparatus.

DETAILED DESCRIPTION

Hereinafter, embodiments will be described.

FIG. 1 is a perspective view showing the exterior of an image formingapparatus 1 according to an embodiment. The image forming apparatus 1has an image forming unit 10 that outputs image information as an outputimage, called hard copy or print out, a paper feeding apparatus 20 thatis capable of feeding a paper (output medium) of an arbitrary size forimage output to the image forming unit 10, and a scanner 50 thatacquires image information to be formed in the image forming unit 10from an object (hereinafter, referred to as original document) includingimage information as image data. The paper feeding apparatus 20 has apaper cassette 201 (shown in FIG. 3) that accommodates papers of anarbitrary size and is attached with respect to the paper feedingapparatus 20. When the original document is sheet-like, the scanner 50is provided with an automatic document feeder 30 that, after imageoutput is formed or image information is read, discharges the readoriginal document from a read position to a discharge position, andguides a next original document to the read position. In addition, aninstruction input unit for instructing the image forming unit 10 tostart image formation or instructing the scanner 50 to read imageinformation of the original document, that is, a control panel 40 isprovided at a predetermined position.

Here, a side on which the paper cassette 201 shown in FIG. 3 is attachedto the paper feeding apparatus 20 is defined as the near side of theimage forming apparatus 1 or the paper feeding apparatus 20. A sideopposite to the side on which the paper cassette 201 shown in FIG. 3 isattached to the paper feeding apparatus 20 is defined as the depth sideof the image forming apparatus 1 or the paper feeding apparatus 20. Apaper discharge tray 60 for discharging a paper printed in the imageforming unit 10 is provided on a side surface of the image formingapparatus 1. A first opening and closing member 70 and a second openingand closing member 80 are provided on a side surface opposite to theside on which the paper discharge tray 60 is provided.

The first opening and closing member 70 is a paper convey unit that isprovided so as to be connected to the image forming unit body 10. Thesecond opening and closing member 80 is a manual paper feed unit that isprovided so as to abut to the first opening and closing member 70.

FIG. 2 is a block diagram showing the control system of the paperfeeding apparatus 20 according to this embodiment.

A control device 2 has a CPU 3, a ROM 4, and a RAM 5. The CPU 3 controlsindividual sensors and motors on the basis of control informationpreviously recorded in the ROM 4. The RAM 5 temporarily recordsnecessary information.

FIG. 3 is a top perspective view of the paper cassette 201 detachablymounted in the paper feeding apparatus 20. An arrow x denotes a mountingdirection with respect to the paper feeding apparatus 20.

The paper feeding apparatus 20 is provided with paper feed rollers 101that, when the paper cassette 201 is inserted, convey a bundle of papersstacked in the paper cassette 201 one by one from the top to the imageforming unit 10. The paper feed rollers 101 convey the paper in a Ydirection perpendicular to an X direction in which the paper cassette201 is inserted into the paper feeding apparatus 20.

Near the positions in contact with the side surfaces on the near anddepth side of a bundle of papers stacked in the paper cassette 201, afront-side sidewall 202F (near side) and a rear-side sidewall 202R(depth side) are provided. The front-side sidewall 202F (near side) andthe rear-side sidewall 202R move in the X direction (hereinafter,referred to as the width direction of the paper cassette 201)perpendicular to the Y direction in which the paper is conveyed.

The front-side sidewall 202F and the rear-side sidewall 202R are formedto be movable, for example, in 1.0 mm pitch by two pinion gears 213 anda pinion gear holding member 212. If one of the front-side sidewall 202Fand the rear-side sidewall 202R moves, the other one moves (describedwith reference to FIG. 26). The front-side sidewall 202F and therear-side sidewall 202R are spaced at a predetermined interval(allowance) in order to eliminate a shift in parallelism with respect tothe Y direction in which the paper set in the paper cassette 201 isconveyed, and regulate the position of the paper in the width direction.

The paper cassette 201 is provided with a pressing plate 203 thatpresses the entire paper against the paper feed rollers 101 from thebottom (bottom surface) of the paper cassette 201 in order to make sureconveyance of the paper by the paper feed rollers 101.

At an end opposite to the paper feed rollers 101 in the Y direction (thelongitudinal direction of the paper cassette 201) in which the paperstacked in the paper cassette 201 is conveyed, an end wall 204 isprovided. The end wall 204 moves back and forth with respect to thelongitudinal direction of the paper cassette 201, and regulates theposition of the paper cassette 201 in the longitudinal direction. An endof the paper in contact with the end wall 204 is referred to as a paperrear end.

FIG. 4 is a bottom perspective view of the paper cassette 201 detachablymounted in the paper feeding apparatus 20. On the rear surface of thepaper cassette 201, a first movable member 205 and a second movablemember 206 are provided. FIGS. 5A and 5B show the shapes of the firstmovable member 205 and the second movable member 206. The first movablemember 205 (or the second movable member 206) has a comb-teeth member2051 (2061) which is arc-shaped and having a plurality of protrusionsand serving as a detection portion. The first movable member 205 (or thesecond movable member 206) has a first joint groove 2052 (2062), a shafthole 2053 (2063), and a second joint groove 2054 (2064).

The first movable member 205 and the second movable member 206 areaxially supported on the rear surface of the paper cassette 201 throughthe shaft hole 2053 and the shaft hole 2063, respectively, so as torotate around a shaft. The rear-side sidewall 202R on the depth sideprovided in the upper surface of the paper cassette 201 and the secondjoint groove 2054 of the first movable member 205 disposed on the rearsurface of the paper cassette 201 are connected by a first connectionmember 207. The rear-side sidewall 202R is threadably mounted from therear-side sidewall 202R side by the first connection member 207.Similarly, the end wall 204 provided in the upper surface of the papercassette 201 and the second joint groove 2064 of the second movablemember 206 disposed on the rear surface of the paper cassette 201 areconnected by a second connection member 208. The end wall 204 isthreadably mounted from the end wall 204 side by the second connectionmember 208. As for the first movable member 205 and the second movablemember 206, the first joint groove 2052 and the second joint groove 2062are connected with each other by the second connection member 208.

FIG. 6 is a top perspective view of the paper cassette 201 detachablymounted in the paper feeding apparatus 20. FIG. 7 is a bottomperspective view of the paper cassette 201 detachably mounted in thepaper feeding apparatus 20.

The paper cassette 201 shown in FIGS. 6 and 7 is in a state where, whena paper of a smaller size than the paper stacked in the paper cassette201 shown in FIGS. 3 and 4 is stacked, the front-side sidewall 202F, therear-side sidewall 202R, and the end wall 204 are moved.

If the front-side sidewall 202F and the rear-side sidewall 202R movefrom the state shown in FIG. 3 and to the state shown in FIG. 6 in adirection to narrow an interval of the paper cassette 201 in the widthdirection, the first connection member 207 rotates the first movablemember 205 around the shaft while moving in the second joint groove2054.

If the end wall 204 moves from the state shown in FIG. 3 to the stateshown in FIG. 6 in a direction to narrow an interval of the papercassette 201 in the longitudinal direction, the second connection member208 rotates the second movable member 206 around the shaft while movingin the second joint groove 2064.

Next, a description will be provided for a first sensor 102 and a secondsensor 103 serving as a detection unit provided on the depth side of thepaper feeding apparatus 20 when the paper cassette 201 is inserted intothe paper feeding apparatus 20. FIG. 8 is a diagram showing the rearsurface of the paper cassette 201 when the paper cassette 201 isinserted into the paper feeding apparatus 20. FIG. 9 is a diagram of thefirst sensor 102 and the second sensor 103 when viewed from the depthside of the paper feeding apparatus 20. FIG. 10 is a diagram of thefirst sensor 102 and the second sensor 103 when viewed from the nearside of the paper feeding apparatus 20.

In the paper feeding apparatus 20, the first sensor 102 is provided at aposition in contact with the comb-teeth member 2051 provided in thefirst movable member 205 on the depth side of the paper feedingapparatus 20 when the paper cassette 201 is inserted into the paperfeeding apparatus 20. In addition, in the paper feeding apparatus 20,the second sensor 103 is provided at a position in contact with thecomb-teeth member 2061 provided in the second movable member 206 on thedepth side of the paper feeding apparatus 20 when the paper cassette 201is inserted into the paper feeding apparatus 20.

The first sensor 102 has four protrusion members 1021 serving asdetection members that protrude from the depth side to the near side.Similarly, the second sensor 103 has four protrusion members 1031 thatprotrude from the depth side to the near side. The CPU 3 discriminatesthe size of the paper cassette 201 in the width direction bycombinations of presses of the four protrusion members 1021 provided inthe first sensor 102. Similarly, the CPU 3 detects the size of the papercassette 201 in the longitudinal direction by combinations of presses ofthe four protrusion members 1031 provided in the second sensor 103. TheCPU 3 discriminates the size of the paper stacked in the paper cassette201 on the basis of the size of the paper cassette 201 in the widthdirection and the size of the paper cassette 201 in the longitudinaldirection.

The first movable member 205 is rotated in accordance with the movementsof the front-side sidewall 202F and the rear-side sidewall 202R, andaccordingly the comb-teeth member 2051 in contact with the first sensor102 is change in shape. Therefore, the first sensor 102 detects the sizeof the paper cassette 201 in the width direction by press patterns ofthe comb-teeth member 2051 on the four protrusion members 1021 providedin the first sensor 102.

Similarly, the second movable member 206 is rotated in accordance withthe movement of the end wall 204, and accordingly the comb-teeth member2061 in contact with the second sensor 103 is changed in shape.Therefore, the second sensor 103 detects the size of the paper cassette201 in the longitudinal direction by press patterns of the comb-teethmember 2061 on the four protrusion members 1031 provided in the secondsensor 103.

In this embodiment, as shown in FIG. 8, the first movable member 205 andthe second movable member 206 are disposed on the rear surface of thepaper cassette 201 on different axes, not on the same axis. A connectionshaft of the first movable member 205 to the paper cassette 201 and aconnection shaft of the second movable member 206 to the paper cassette201 are provided to be arranged along the width direction of the papercassette 201, which is the horizontal direction of the image formingapparatus 1.

As shown in FIG. 10, the first sensor 102 and the second sensor 103 havethe same shape. The first sensor 102 has four protrusion members 1021provided on a boxlike member 1022, in which a board is incorporated, inthe horizontal direction of the image forming apparatus 1. The secondsensor 103 has four protrusion members 1031 provided on a boxlike member1032, in which a board is incorporated, in the horizontal direction ofthe image forming apparatus 1.

The protrusion members 1021 have a columnar shape having a diametersmaller than the height of the boxlike member 1022 of the first sensor102. The boxlike member 1022 of the first sensor 102 has a height equalto or larger than the thickness of the first movable member 205.Similarly, the protrusion members 1031 have a columnar shape having adiameter smaller than the height of the boxlike member 1032 of thesecond sensor 103. The boxlike member 1032 of the second sensor 103 hasa height equal to larger than the thickness of the second movable member206.

For this reason, if the first sensor 102 and the second sensor 103 arearranged in the height direction on the same axis of the paper feedingapparatus 20, the boxlike member 1022 of the first sensor 102 and theboxlike member 1022 of the second sensor 103 are superimposed andincrease in height. In this embodiment, as shown in FIG. 10, the shaftof the first movable member 205 and the shaft of the second movablemember 206 are provided to be arranged along the width direction of thepaper cassette 201. A position where the comb-teeth member 2051 of thefirst movable member 205 is opposed to the first sensor 102 and aposition where the comb-teeth member 2061 of the second movable member206 is opposed to the second sensor 103 are shifted in the horizontaldirection.

As shown in FIG. 10, the first sensor 102 and the second sensor 103 areprovided on the depth side of the paper feeding apparatus 20 to beshifted in the horizontal direction at positions not opposed to eachother in the height direction. The first sensor 102 and the secondsensor 103 are provided so as to at least partially overlap each otherin the horizontal direction.

An interval a between a center axis in the horizontal direction of theprotrusion members 1022 arranged in the first sensor 102 and a centeraxis in the horizontal direction of the protrusion members 1032 arrangedin the second sensor 103 is narrowed, as compared with a case where thefirst sensor 102 and the second sensor 103 are disposed to overlap eachother in the height direction. Therefore, the paper cassette 201 isreduced in height, as compared with the related art example.

The first movable member 205 and the second movable member 206 aredisposed in the paper cassette 201 to be axially shifted in the widthdirection of the paper cassette 201. However, since the paper cassette201 has a size corresponding to a paper of a stackable maximum size,even if the first movable member 205 and the second movable member 206are axially shifted in the width direction of the paper cassette 201,there is no case where the structure is increased in size.

Next, a second embodiment will be described. FIG. 11 is a diagramshowing a sensor board 300 which is disposed on the depth side of thepaper feeding apparatus 20 and on which the first sensor 102 and thesecond sensor 103 are provided.

The first sensor 102 and the second sensor 103 are arranged on the samesensor board 300 in the horizontal direction. The sensor board 300 isstructurally detachably fixed and electrically connected to a housing 11of the paper feeding apparatus 20 so as to be detachable from. Thesensor board 300 is adapted to be electrically connected to the paperfeeding apparatus 20. FIG. 12 shows the sensor board 300 that is held bythe housing 11 of the paper feeding apparatus 20. The sensor board 300is mounted with respect to the housing 11 from the near side of thepaper feeding apparatus 20 to the depth side. The sensor board 300 has afirst claw member 313 and a second claw member 314. The first clawmember 313 is a plate spring that has elasticity in a directionperpendicular to the mounting direction of the sensor board 300. Thesecond claw member 314 has the same structure as the first claw member313. In addition, the first claw member 313 has an opening 3131 of apredetermined size. The second claw member 314 also has an opening 3141of a predetermined size.

As shown in FIG. 12, the first movable member 205 has a first sensorboard holding portion 2055 in a part of the comb-teeth member 2051, andthe second movable member 206 has a second sensor board holding portion2065 in a part of the comb-teeth member 2061.

A front end of the first sensor board holding portion 2055 is engagedwith an opening 3131 provided in the first claw member 313 in a shapesmaller than the opening 3131. In addition, the front end of the firstsensor board holding portion 2055 is moved to a position opposed to theopening 3131 provided in the first claw member 313 by rotation of thefirst movable member 205. Similarly, a front end of the second sensorboard holding portion 2065 is engaged with an opening 3141 provided inthe second claw member 314 in a shape smaller than the opening 3141. Inaddition, the front end of the second sensor board holding portion 2065is moved to a position opposed to the opening 3141 provided in thesecond claw member 314 by rotation of the second movable member 206.

FIG. 13 shows a state where the front-side sidewall 202F, the rear-sidesidewall 202R, and the end wall 204 are moved to predeterminedpositions, and the second sensor board holding portion 2065 is engagedwith the opening 3141 provided in the second claw member 314. If thefront-side sidewall 202F and the rear-side sidewall 202R are moved inthe width direction of the paper cassette 201, the first movable member205 is rotated around the shaft in accordance with the movement. Forthis reason, when the front-side sidewall 202F and the rear-sidesidewall 202R are opened in the width direction of the paper cassette201, as shown in FIG. 12, the first sensor board holding portion 2055 isengaged with the opening 3131 provided in the first claw member 313.

Similarly, if the end wall 204 is moved in the longitudinal direction ofthe paper cassette 201, the second movable member 206 is rotated aroundthe shaft in accordance with the movement. For this reason, when the endwall 204 is opened in the longitudinal direction of the paper cassette201, as shown in FIG. 13, the second sensor board holding portion 2065is engaged with the opening 3141 of the first claw member 314. Inaddition, if the end wall 204 is opened full in the longitudinaldirection of the paper cassette 201, the second sensor board holdingportion 2065 bends the second claw member 314 in a direction away fromthe housing 11. Similarly, if the front-side sidewall 202F and therear-side sidewall 202R are opened full in the width direction of thepaper cassette 201, the first sensor board holding portion 2055 bendsthe second claw member 313 in a direction away from the housing 11.

FIG. 15 is a diagram showing coupling of the first movable member 205and the second movable member 206, and the sensor board 300 when viewedfrom the upper surface. FIG. 16 is a diagram showing coupling of thefirst movable member 205 and the second movable member 206, and thesensor board 300 when viewed from the lower surface. If the front-sidesidewall 202F, the rear-side sidewall 202R, and the end wall 204 aremoved to predetermined positions, the first sensor board holding portion2055 is engaged with the first claw member 313, and the second sensorboard holding portion 2065 is engaged with the second claw member 314.As shown in FIGS. 15 and 16, the sensor board 300 is held by the firstsensor board holding portion 2055 and the second sensor board holdingportion 2065. Then, as shown in FIG. 14, the sensor board 300 is spacedaway from the housing 11 by the first sensor board holding portion 2055and the second sensor board holding portion 2065.

In this state, if a serviceman draws out the paper cassette 201 from thepaper feeding apparatus 20, the sensor board 300 is drawn out togetherwith the first movable member 205 and the second movable member 206 in astate where the sensor board 300 is held by the first movable member 205and the second movable member 206. To the contrary, if the servicemaninserts the paper cassette 201 into the image forming apparatus 1 in astate where the sensor board 300 is held by the first movable member 205and the second movable member 206, the sensor board 300 is placed at apredetermined position in the paper feeding apparatus 20.

If the end wall 204 is in a state other than the full opened state inthe longitudinal direction of the paper cassette 201, as shown in FIG.13, the second claw member 314 returns to a hold position with respectto the housing 11. Similarly, when the front-side sidewall 202F and therear-side sidewall 202R are in a state other than the full opened statein the width direction of the paper cassette 201, the first claw member313 returns to a hold position with respect to the housing 11. It iseasy for the serviceman to detach and attach the sensor board 300 withrespect to the paper feeding apparatus 20.

FIG. 17 is a flowchart showing the flow of detachment of the sensorboard 300.

First, the serviceman sets the end wall 204, the front-side sidewall202F, and the rear-side sidewall 202R of the paper cassette 201 atpredetermined positions (Act 101).

Next, the serviceman mounts the paper cassette 201 in the paper feedingapparatus 20 (Act 102). The serviceman puts the end wall 204 in the fullopened state in the longitudinal direction of the paper cassette 201,and puts the front-side sidewall 202F and the rear-side sidewall 202R inthe full opened state in the width direction of the paper cassette 201.The first movable member 205 and the second movable member 206 rotatearound the shaft (Act 103).

Since the first movable member 205 and the second movable member 206hold the sensor board 300, the serviceman can draw out the sensor board300 from the paper feeding apparatus 20 together with the paper cassette201 (Act 104).

Next, a third embodiment will be described.

FIG. 18 is a perspective view of the paper cassette 201 and the sensorboard 300 mounted in the paper feeding apparatus 20 when viewed from thedepth side of the paper feeding apparatus 20. In the paper feedingapparatus 20, guide rail members 12 for holding the paper cassette 201mountable on the paper feeding apparatus 20 and enabling the papercassette 201 to be drawn out from the paper feeding apparatus 20 areprovided in the housing 11. The sensor board 300 is disposed on thedepth side of the paper feeding apparatus 20 opposed to the papercassette 201. The paper cassette 201 is positioned with respect to thehousing 11.

FIG. 19 shows the structure of the sensor board 300 according to thisembodiment. The sensor board 300 has a holder member 311 and a floatmember 304 in combination. The holder member 311 has a positioningmember 303, a first holder boss 305, and a second holder boss 306. Thepositioning member 303 is engaged with the housing 11 of the paperfeeding apparatus 20. For this reason, the absolute position of theholder member 311 with respect to the paper feeding apparatus 20 isfixed. The first holder boss 305 and the second holder boas 306 areprotrusions. The float member 304 is provided with an opening 307, anopening 308, an opening 309, and an opening 310. The opening 309 has ashape extending in the horizontal direction. In the float member 304,the first sensor 102 and the second sensor 103 are provided as a singlebody.

The first holder boss 305 that is a protrusion provided in the holdermember 311 is fitted into the opening 307 of the float member 304. Thesecond holder boss 306 that is a protrusion provided in the holdermember 311 is fitted into the opening 308 of the float member 304. Theopening 307 and the opening 308 have a diameter larger than those of thefirst holder boss 305 and the second holder boss 306, respectively.Therefore, the float member 304 has a degree of freedom with respect tothe holder member 311. As shown in FIG. 20, the float member 304 isfixed by a plurality of fixing portions 3111 provided in the holdermember 311, and the movement of the float member 304 in the front-backdirection is limited. Therefore, the float member 304 that is made of aplate has a degree of freedom in the holder member 311 in a directionindicated by an arrow in the drawing.

FIG. 21 is a diagram showing the rear surfaces of the sensor board 300and the paper cassette 201. On a surface of the paper cassette 201opposed to the sensor board 300, a first boss 209 and a second boss 210protrude in an extension direction. The float member 304 has at leastopenings corresponding to or more than the number of bosses provided inthe paper cassette 201. The first boss 209 is fitted into the opening310 provided in the float member 304. The second boss 210 is fitted intothe opening 309 provided in the float member 304. The first boss 209 andthe second boss 210 have a slim shape along the extension direction soas to be easily guided to the opening 310 and the opening 309,respectively. The opening 310 and the opening 309 are purled such thatthe first boss 209 and the second boss 210 are easily fitted thereinto.

If the paper cassette 201 is inserted with the sensor board 300 fixed tothe housing 11 of the paper feeding apparatus 20, the first boss 209 andthe second boss 210 are individually fitted into the opening 310 and theopening 309 of the sensor board 300. The opening 310 and the opening 309are provided in the float member 304. In the float member 304, the firstsensor 102 and the second sensor 103 are provided as a single body.

Therefore, as shown in FIG. 22, the first movable member 205 and thesecond movable member 206 provided in the paper cassette 201 areconstantly accurately opposed to the first sensor 102 and the secondsensor 103, respectively. That is, the relative positional relationshipbetween the first movable member 205 and the first sensor 102 and therelative positional relationship between the second movable member 206and the second sensor 103 are constantly uniform by the float member304. The correlation of the first movable member 205 and the firstsensor 102, and the correlation of the second movable member 206 and thesecond sensor 103 are secured. Therefore, there is no case where thefirst sensor 102 and the second sensor 103 perform erroneous detection.

The first boss 209 provided in the paper cassette 201 is fitted into theopening 310 to position the float member 304. The second boss 210provided in the paper cassette 201 is fitted into the opening 309 toposition the float member 304 in the vertical direction and to suppressrotation of the float member 304.

In the related art, the first sensor 102 and the second sensor 103 arefixed to the housing 11. For this reason, the first movable member 205and the first sensor 102 and the second movable member 206 and thesecond sensor 103 have a variation in the relative positionalrelationship due to a cumulative tolerance, assembling accuracy, andpart accuracy caused by a lot of parts between parts in contact witheach other.

According to the sensor board 300 of this embodiment, the relativepositions of the first sensor 102 and the second sensor 103 are reliablydetermined with respect to the paper cassette 201 by an inexpensive andsimple method. For this reason, it is possible to avoid erroneousdetection due to misalignment of the first sensor 102 and the secondsensor 103.

The first boss 209 and the second boss 210 are individually fitted intothe opening 310 and the opening 309 provided in the float member 304.Therefore, with the degree of freedom of the float member 304, the papercassette 201 can be easily inserted and drawn out. As a result, theuser's operational load in inserting and drawing out the paper cassette201 is reduced.

Next, a fourth embodiment will be described.

FIG. 23 is an enlarged view of the front-side sidewall 202F in the papercassette 201 shown in FIG. 3. FIG. 24 is an enlarged view of therear-side sidewall 202R in the paper cassette 201 shown in FIG. 3. FIG.25 is an enlarged view of the end wall 204 in the paper cassette 201shown in FIG. 3.

As shown in FIGS. 23, 24, and 25, paper sensors 211 are individuallyprovided on the wall surfaces near at least one of the front-sidesidewall 202F, the rear-side sidewall 202R, and the end wall 204. As thepaper sensors 211, for example, an actuator is used. If the front-sidesidewall 202F and the rear-side sidewall 202R are moved in accordancewith the size of the paper stacked in the paper cassette 201, the papersensors 211 are in contact with the paper, and the CPU 3 determines thatthe front-side sidewall 202F and the rear-side sidewall 202R are movedto positions to come into contact with the paper. The same is applied tothe paper sensor 211 provided on the end wall 204. The paper sensors 211may be a non-contact sensor, for example, a reflection-type sensor or adistance measurement sensor.

Even though the CPU 3 determines the paper size from the detectionresults of the first sensor 102 and the second sensor 103, when thepaper sensors 211 determine paper absence, the CPU 3 determines that apaper of a different size (small size) from the paper size detected fromthe combination of the detection results of the first sensor 102 and thesecond sensor 103 is stacked. The CPU 3 displays on the control panel 40serving as a notification unit a purport to urge the user to correctlyset the front-side sidewall 202F and the rear-side sidewall 202R or theend wall 204.

With the above configuration, the user can reliably set the front-sidesidewall 202F and the rear-side sidewall 202R or the end wall 204 forthe paper stacked in the paper cassette 201. Therefore, the paper sizedetected by the CPU 3 from the combination of the detection results ofthe first sensor 102 and the second sensor 103 is consistent with thesize of the paper stacked in the paper cassette 201.

A description will now be provided for a case where the user stacks apaper of an irregular size in the paper cassette 201, and reliably setsthe front-side sidewall 202F and the rear-side sidewall 202R, and theend wall 204 for the paper. The RAM 5 records combinations of detectionpatterns of the first sensor 102 and the second sensor 103 in advance.Then, the CPU 3 discriminates the paper size by comparing thecombination of detection patterns of the first sensor 102 and the secondsensor 103 and size associated information in which combinations ofdetection patterns recorded in the RAM 5 are associated with papersizes. The irregular size refers to a paper size that the CPU 3 cannotdiscriminate by comparison of the combination of the detection patternsof the first sensor 102 and the second sensor 103 with informationrecorded in the RAM 5.

Therefore, when the CPU 3 determines that the detection results of thefirst sensor 102 and the second sensor 103 are not associated withinformation recorded in the RAM 5 (not a regular size), the CPU 3displays on the control panel 40 a purport that the paper size cannot bediscriminated.

The user inputs the paper size in accordance with the display on thecontrol panel 40. The CPU 3 records the input paper size in the RAM 5 inassociation with the combination of detection patterns of the firstsensor 102 and the second sensor 103. Thereafter, if the user stacks apaper of a corresponding size in the paper cassette 201, and reliablysets the front-side sidewall 202F and the rear-side sidewall 202R, andthe end wall 204 for the paper, the CPU 3 can reliably detect the papersize by comparing the combination of detection patterns of the firstsensor 102 and the second sensor 103 with information recorded in theRAM 5. Therefore, as described above, if the user inputs a paper size atone time, when the user stacks a paper of an irregular size in the papercassette 201, it is not necessary for the control panel 40 to set thepaper size.

FIG. 26 is a flowchart collectively showing the flow of this process.

First, the user stacks a paper in the paper cassette 201 and moves thefront-side sidewall 202F, the rear-side sidewall 202R, and the end wall204 in accordance with the paper size. The paper sensors 211 attached atpredetermined positions of the end wall 204, the front-side sidewall202F, and the rear-side sidewall 202R detect whether or not a paper ispresent therearound, and determines whether or not the front-sidesidewall 202F, the rear-side sidewall 202R, and the end wall 204 are setin accordance with the paper size (Act 201).

If the paper sensors 211 determine that the end wall 204 (or thefront-side sidewall 202F and the rear-side sidewall 202R) are correctlyset (Act 201, YES), the CPU 3 determines whether or not a combination ofdetection patterns of the first sensor 102 and the second sensor 103 isassociated with information on paper size recorded in the RAM 5 (Act202).

When the CPU 3 can discriminate the paper size (Act 202, YES), the CPU 3conveys the paper by the paper feed rollers 101 driven by a paper feedroller motor 400 (Act 203).

If the paper sensor 211 determines that the end wall 204 (or thefront-side sidewall 202F and the rear-side sidewall 202R) are notcorrectly set (Act 201, NO), the CPU 3 displays on the control panel 40a purport to urge the user to correctly set the end wall 204 (or thefront-side sidewall 202F and the rear-side sidewall 202R) in accordancewith the paper (Act 204).

After the paper cassette 201 is drawn out from the paper feedingapparatus 20, if the CPU 3 determines that the paper cassette 201 isinserted into the paper feeding apparatus 20 again (Act 205), theprocess returns to Act 201.

When the paper size cannot be discriminated (Act 202, NO), the CPU 3displays on the control panel 40 a purport that a paper of an irregularsize is stacked (Act 206). That is, the user can draw out the papercassette 201 to confirm whether or not the size of the paper stacked inthe paper cassette 201 is an intended size.

The user draws out the paper cassette 201, determines that the end wall204 (or the front-side sidewall 202F and the rear-side sidewall 202R)are not correctly set in accordance with the paper, selects NO (Act 207,NO), and correctly sets the end wall 204 (or the front-side sidewall202F and the rear-side sidewall 202R). Then, if it is determined thatthe paper cassette 201 is inserted into the paper feeding apparatus 20again (Act 208), the process returns to Act 201.

When the user draws out the paper cassette 201 and determines that theend wall 204 (or the front-side sidewall 202F and the rear-side sidewall202R) are correctly set in accordance with the paper (Act 207, YES), ifthe CPU 3 determines that the paper size is not correct (Act 209, NO),the user inputs the paper size in accordance with the display on thecontrol panel 40 (Act 211). The CPU 3 records the input paper size inthe RAM 5 in association with a combination of detection patterns of thefirst sensor 102 and the second sensor 103 (Act 211). If the CPU 3determines that the paper size is correct (Act 209, YES), the CPU 3conveys the paper by the paper feed rollers 101 driven by the paper feedroller motor 400 (Act 210).

With this configuration, when a paper of a size different from the papersize determined by the CPU 3 is stacked in the paper cassette 201, anerror is displayed on the control panel 40. Therefore, a paper of adifferent size is not conveyed to the image forming unit 10. As aresult, in the image forming unit 10, it is possible to prevent paperjam or deterioration in printing position accuracy from occurring due toa difference in paper size.

Next, a fifth embodiment will be described. FIG. 27 is a top perspectiveview of a part of the paper cassette 201 shown in FIG. 3. Here, thefront-side sidewall 202F has a front-side rack portion 2021 that has apredetermined length in the width direction of the paper cassette 201.The rear-side sidewall 202R has a rear-side rack portion 2022 that has apredetermined length in the width direction of the paper cassette 201.The front-side rack portion 2021 and the rear-side rack portion 2022 arearranged in parallel to be spaced at a predetermined interval from eachother. Two pinion gears 213 are disposed between the front side rackportion 2021 and the rear-side rack portion 2022. In order to fix thepinion gears 213, a pinion gear holding member 212 serving as a positioncorrection member is disposed on the upper surface of the pinion gear213 and fixed to the paper cassette 201.

FIGS. 28 and 29 show connection of the rear-side sidewall 202R and thefirst movable member 205 when viewed from the rear surface of the papercassette 201. To the rear-side sidewall 202R, a first connection member207 that protrudes toward the rear surface of the paper cassette 201 isfixed by a screw 214. The first connection member 207 is fitted into asecond joint groove 2054 provided in the first movable member 205.Accordingly, the first movable member 205 is rotated around the shaft inaccordance with the operation of the first connection member 207 bymovement of the rear-side sidewall 202R in the width direction of thepaper cassette 201.

FIG. 30 is a diagram showing a state the front-side sidewall 202F andthe rear-side sidewall 202R are stretched in the width direction of thepaper cassette 201. FIG. 31 is a diagram showing a case where thefront-side sidewall 202F and the rear-side sidewall 202R are retractedin the width direction of the paper cassette 201. The two pinion gears213 are disposed between the front-side rack portion 2021 and therear-side rack portion 2022. In the front-side rack portion 2021 and therear-side rack portion 2022, grooves are provided at a regular intervalon opposing sides along the longitudinal direction. The pinion gears 213are fitted between the front-side rack portion 2021 and the rear-siderack portion 2022. Grooves that are provided in the outer peripheralsurfaces of the pinion gears 213 at a regular interval are meshed withthe groove in the front-side rack portion 2021 and the groove in therear-side rack portion 2022. The pinion gears 213 are fixed to the papercassette 201 by the pinion gear holding member 212. Therefore, thepositional relationship between the pinion gears 213 and the papercassette 201 are fixed. As a result, if the front-side sidewall 202Fmoves in the width direction, the rear-side sidewall 202R also movesfrom the center axis of the paper tray 20 in the longitudinal directionby the same interval as the movement interval of the front-side sidewall202F through the pinion gears 213.

FIG. 32 is a top perspective view of the paper cassette 201. FIG. 33 isa diagram showing the paper cassette 201 in a state where the piniongears 213 and the pinion gear holding member 212 are mounted in thepaper cassette 201. FIG. 34 is a diagram of the paper cassette 201 whenthe pinion gears 213 and the pinion gear holding member 212 aredisassembled from the paper cassette 201. FIG. 35 is a diagram showing astate where the pinion gears 213 are mounted in the paper cassette 201,and a surface (rear surface) of the pinion gear holding member 212opposed to the paper cassette 201.

In the paper cassette 201 sandwiched between the front-side rack portion2021 and the rear-side rack portion 2022, a first fixing portion 215 anda second fixing portion 216 are provided to be spaced at a predeterminedinterval from each other in the width direction of the paper cassette201. The first fixing portion 215 is provided at a position near thefront-side sidewall 202F. The second fixing portion 216 is provided at aposition near the rear-side sidewall 202R. In the first fixing portion215 and the second fixing portion 216, grooves are provided at a regularinterval (here, 1 mm) along the width direction of the paper cassette201.

On the rear surface of the pinion gear holding member 212, as shown inFIG. 35, a first correction member 2121 is provided to be opposed to thefirst fixing portion 215 provided in the paper cassette 201. Inaddition, on the rear surface of the pinion gear holding member 212, asecond correction member 2122 is provided to be opposed to the secondfixing portion 216 provided in the paper cassette 201. In the firstcorrection member 2121 and the second correction member 2122, groovesare formed at a regular interval (here, 1 mm) along the width directionof the paper cassette 201 when being mounted in the paper cassette 201.

On the rear surface of the pinion gear holding member 212, two holdingprotrusions 2123 are provided between the first correction member 2121and the second correction member 2122 along the width direction of thepaper cassette 201 when being mounted in the paper cassette 201. The twoholding protrusions 2123 provided in the pinion gear holding member 212hold the pinion gears 213, respectively, when the pinion gear holdingmember 212 is mounted in the paper cassette 201. In addition, on therear surface of the pinion gear holding member 212, a position fixingprotrusion 2124 is provided at the center in the width direction of thepaper cassette 201 when being mounted in the paper cassette 201. Theposition fixing protrusion 2124 provided in the pinion gear holdingmember 212 is fitted into a fixing hole 219 when the pinion gear holdingmember 212 is mounted in the paper cassette 201. The first correctionmember 2121 of the pinion gear holding member 212 is fastened to theopposing first fixing portion 215 by a screw 217. Similarly, the secondcorrection member 2122 of the pinion gear holding member 212 is fastenedto the opposing second fixing portion 216 by a screw 218.

FIGS. 36 and 37 are sectional views taken along the line C-C of FIG. 35in the width direction of the paper cassette 201. In the first fixingportion 215, a plurality of grooves are provided at intervals of 1 mmalong the width direction of the paper cassette 201. The serrated teethat regular intervals provided in the first fixing portion 215 and thesecond fixing portion 216 define a movement pitch of lateralmisalignment correction (described below) by the pinion gear holdingmember 212.

The position fixing protrusion 2124 provided in the pinion gear holdingmember 212 is fitted into the fixing hole 219 of the paper cassette 201,and the pinion gear holding member 212 is fixed to the paper cassette201. This fixed state is defined as a normal state. In the normal state,when the paper is stacked in the paper cassette 201, the front-sidesidewall 202F and the rear-side sidewall 202R arrange the paper suchthat the just center of the paper cassette 201 in the width directionbecomes the center axis of the paper in the longitudinal direction.

Next, lateral misalignment correction of the paper by the pinion gearholding member 212 will be described. FIG. 38 is a diagram showing thepaper cassette 201 in a state where the pinion gears 213 and the piniongear holding member 212 are mounted in the paper cassette 201. FIG. 39is a diagram showing the rear surface of the pinion gear holding member212. FIG. 40 is a diagram showing lateral misalignment correction by thepinion gear holding member 212.

Here, a description will be provided for a case where the paper stackedin the paper cassette 201 is shifted by 1 mm to the depth side (an arrowdirection of FIG. 38) of the paper cassette 201. As shown in FIG. 35,the position fixing protrusion 2124 is provided on the rear surface ofthe pinion gear holding member 212. The pinion gear holding member 212is fixed to the paper cassette 201 in a state where the position fixingprotrusion 2124 is provided on the rear surface of the pinion gearholding member 212 in the normal state. The position fixing protrusion2124 is removed from the pinion gear holding member 212 shown in FIG.39. Therefore, the user can fix the pinion gear holding member 212 withthe position fixing protrusion 2124 removed to be shifted in the widthdirection of the paper cassette 201.

Here, the pinion gear holding member 212 is provided with a movementdistance measurement member 221 at an end near the rear-side sidewall202R in the width direction of the paper cassette 201. A front end ofthe movement distance measurement member 221 is shaped to beperpendicular to the width direction of the paper cassette 201. As shownin FIG. 40, at a predetermined position in the width direction of thepaper cassette 201, a scale unit 221 is provided between the secondfixing portion 216 and the rear-side sidewall 202R. The scale unit 221has scale marks provided at regular intervals (here, 1 mm) in the widthdirection of the paper cassette 201, similarly to the first fixingportion 215 and the second fixing portion 216.

A left view in FIG. 40 shows a case where in the normal state, thepinion gear holding member 212 is fixed to the paper cassette 201. Thefront end of the movement distance measurement member 221 of the piniongear holding member 212 is located at a reference scale mark as apredetermined reference position of the scale unit 221.

A center view of FIG. 40 illustrates movement of the pinion gear holdingmember 212 when lateral misalignment correction is performed to shiftthe paper stacked in the paper cassette 201 by 1 mm toward the depthside of the paper cassette 201. Usually, the rear-side sidewall 202R andthe front-side sidewall 202F move in the width direction of the papercassette 201 with the pinion gear holding member 212 and the piniongears 213 fixed to the pinion gear holding member 212 as a center.Therefore, if the positions of the pinion gear holding member 212 andthe pinion gears 213 fixed to the pinion gear holding member 212 in thewidth direction of the paper cassette 201 are shifted, the front-sidesidewall 202F and the rear-side sidewall 202R arrange the paper suchthat the position shifted from the center in the width direction of thepaper cassette 201 becomes the center axis in the longitudinal directionof the paper. This is lateral misalignment correction.

The first fixing portion 215, which is opposed to the first correctionmember 2121 provided in the pinion gear holding member 212, and thesecond fixing portion 216, which is opposed to the second correctionmember 2122 provided in the pinion gear holding member 212, are providedwith grooves at an interval of 1 mm. Therefore, the user can move thepinion gear holding member 212 and the pinion gears 213 fixed to thepinion gear holding member 212 in an interval of 1 mm.

If the user moves the pinion gear holding member 212 and the piniongears 213 fixed to the pinion gear holding member 212 by 1 mm toward therear-side sidewall 202R, the front end of the movement distancemeasurement member 221 of the pinion gear holding member 212 is locatedat a scale mark ahead of the predetermined reference scale mark of thescale unit 221 by 1 mm.

A right view of FIG. 40 illustrates movement of the pinion gear holdingmember 212 when lateral misalignment correction is performed to shiftthe paper stacked in the paper cassette 201 by 2 mm toward the depthside of the paper cassette 201. Similarly, if the user moves the piniongear holding member 212 and the pinion gears 213 fixed to the piniongear holding member 212 by 2 mm toward the rear-side sidewall 202R, thefront end of the movement distance measurement member 221 of the piniongear holding member 212 is located at a scale mark ahead of thepredetermined reference scale mark of the scale unit 221 by 2 mm.

Therefore, the user can read the value of the scale unit 221 indicatedby the front end of the movement distance measurement member 221,thereby easily viewing how much lateral misalignment correction is made.

Here, when the user moves the pinion gear holding member 212 to performlateral misalignment correction on the front-side sidewall 202F and therear-side sidewall 202R, the first movable member 205 connected to therear-side sidewall 202R by the first connection member 207 rotates at adifferent rotation angle from that in the normal state. Therefore, in astate where lateral misalignment correction is made, a press pattern ofthe comb-teeth member 2051 of the first movable member 205 against thefour protrusion members 1021 is different from a press pattern of thecomb-teeth member 2051 of the first movable member 205 against the fourprotrusion members 1021 in the normal state. The first sensor 102 mayerroneously detect the size of the paper cassette 201 in the widthdirection in a state where lateral misalignment correction is made.

In this embodiment, the first movable member 205 in a state wherelateral misalignment correction is made is moved to a position differentfrom the first movable member 205 in the normal state.

FIG. 41 is a diagram of the first movable member 205 and the firstconnection member 207 when viewed from the rear surface of the papercassette 201. FIG. 42 is a diagram showing lateral misalignmentcorrection of the first movable member 205 by the first connectionmember 207. FIG. 42 is a sectional view taken along the line E-E of FIG.41.

As shown in FIG. 28, the first connection member 207 that protrudestoward the rear surface of the paper cassette 201 is fixed by the screw214. Then, as shown in FIG. 41, the first connection member 207 isfitted into the second joint groove 2054 provided in the first movablemember 205.

Here, on the surface of the rear-side sidewall 202R which the firstconnection member 207 is in contact with, a groove 222 is provided at aregular interval (here, 1 mm) along the same direction as the movementdirection of the front-side sidewall 202F and the rear-side sidewall202R.

As shown in FIG. 42, on the surface of the first connection member 207which the rear-side sidewall 202R is in contact with, a groove portion2071 is also provided at a regular interval (here, 1 mm). That is, thegroove 222 of the rear-side sidewall 202R and a groove provided in thegroove portion 2071 of the first connection member 207 are the sameinterval as the grooves provided in the first fixing portion 215 and thesecond fixing portion 216, and the interval between the scale marksprovided in the scale unit 221.

A left view of FIG. 43 shows a state where in the normal state, thefirst connection member 207 is fitted into the groove 222 of therear-side sidewall 202R. In the normal state, a protrusion 2072 that isprovided at a predetermined reference position of the first connectionmember 207 is fitted into a cutout 2023 provided at a predeterminedposition of the rear-side sidewall 202R.

A center view of FIG. 43 illustrates movement of the first connectionmember 207 when lateral misalignment correction is performed to shiftthe paper stacked in the paper cassette 201 by 1 mm toward the depthside of the paper cassette 201. The user can draw out the protrusion2072 of the first connection member 207, thereby moving the firstconnection member 207 in a direction in which the groove 222 of therear-side sidewall 202R is provided. In this case, the user can move thefirst connection member 207 from the reference position by 1 mm in adirection from the front-side sidewall 202F toward the rear-sidesidewall 202R.

When the pinion gear holding member 212 and the pinion gears 213 fixedto the pinion gear holding member 212 are moved from the referenceposition by 1 mm, the first connection member 207 is also moved from thereference position by 1 mm. Therefore, the first sensor 102 acquires thesame pattern as that when in the normal state, the comb-teeth member2051 of the first movable member 205 presses the four protrusion members1021.

A right view of FIG. 43 illustrates movement of the first connectionmember 207 when lateral misalignment correction is performed to shiftthe paper stacked in the paper cassette 201 by 2 mm toward the depthside of the paper cassette 201. In this case, the user can move thefirst connection member 207 by 2 mm from the reference position in adirection from the front-side sidewall 202F toward the rear-sidesidewall 202R.

When the pinion gear holding member 212 and the pinion gears 213 fixedto the pinion gear holding member 212 are moved from the referenceposition by 2 mm, the first connection member 207 is also moved from thereference position by 2 mm. Therefore, the first sensor 102 acquires thesame pattern as that when in the normal state, the comb-teeth member2051 of the first movable member 205 presses the four protrusion members1021.

As described above, the user moves the first connection member 207 bythe same distance according to the movement of the pinion gear holdingmember 212 and the pinion gears 213 fixed to the pinion gear holdingmember 212. Therefore, even if lateral misalignment correction is made,there is no case where the first sensor 102 erroneously detects thepaper size. In addition, what is necessary is that the user moves thepinion gear holding member 212 and the first connection member 207 bythe same distance. Therefore, it is possible to suppress the occurrenceof erroneous detection due to a variation in lateral misalignmentcorrection.

The protrusion 2072 provided in the first connection member 207 is usedto hold the position of the first connection member 207 in the normalstate. For this reason, there is no case where the first connectionmember 207 is erroneously attached when assembling. Therefore, there isno case where the first sensor 102 erroneously detects the paper sizedue to an error in assembling. In addition, for lateral misalignmentcorrection of the paper, it is necessary for the user to bend (remove)the position fixing protrusion 2124 of the pinion gear holding member212 and the protrusion 2072 of the first connection member 207. For thisreason, it is possible to prevent the user from executing the lateralmisalignment correction of the paper more than necessary, and it ispossible to make the user to recognize that both the pinion gear holdingmember 212 and the first connection member 207 need to be moved in sets.

In this embodiment, the first connection member 207 is fixed to the rearsurface of the rear-side sidewall 202R, but it may be fixed so as tomovable with respect to the groove portion 2071 provided in the uppersurface of the rear-side sidewall 202R.

Next, a sixth embodiment will be described. Here, a case where lateralmisalignment correction of the paper by the pinion gear holding member212 shown in FIG. 40 is made will be described. In the fifth embodiment,the first movable member 205 in which lateral misalignment correction isperformed is moved to a different position from the position of thefirst movable member 205 in the normal state, but in the sixthembodiment, as shown in FIG. 44, the sensor board 300, that is, thefirst sensor 102 is shifted by the first link member 220.

The link member 220 is, for example, a rod-shaped member that isconnected to the pinion gear holding member 212. The link member 220 isprovided in a direction from the front-side sidewall 202F toward therear-side sidewall 202R, and extends to a position beyond the paper tray20. As shown in the center view of FIG. 40, if the user moves the piniongear holding member 212 toward the rear-side sidewall 202R, the firstlink member 220 is moved by the same distance in the same direction inconnection with the pinion gear holding member 212.

Here, the sensor board 300 is provided in the housing 11 of the imageforming apparatus 1. The sensor board 300 is provided in the housing 11such that the first sensor 102 and the second sensor 103 are moved inthe movement direction of the first link member 220, that is, in adirection perpendicular to the rear-side sidewall 202R and the end wall204.

Since the first link member 220 is in contact at 45 degrees with asecond link member 312 at a predetermined place of the sensor board 300,the sensor board 300 is moved by the same distance in accordance withthe movement of the first link member 220. Therefore, when the userexecutes lateral misalignment correction by using the pinion gearholding member 212, the first link member 220 is also move in the samedirection. The first link member 220 moves the sensor board 300, andthus it is possible to prevent the first sensor 102 of the sensor board300 from erroneously detecting the size of the paper cassette 201 in thewidth direction when lateral misalignment correction is made. The firstlink member 220 moves the sensor board 300, thereby correcting an errorin size detection due to lateral misalignment correction.

Next, other examples will be described. As shown in FIG. 45, the piniongear holding member 212 is provided with a lateral misalignmentdetection unit 221. The lateral misalignment detection unit 221 detectsthe amount of movement from the normal state if the pinion gear holdingmember 212 is moved from the normal state.

If the pinion gear holding member 212 is moved from the normal state forlateral misalignment correction, a press pattern of the comb-teethmember 2051 of the first movable member 205 against the four protrusionmembers 1021 is different from a press pattern of the comb-teeth member2051 of the first movable member 205 against the four protrusion members1021 in the normal state.

Here, when the pinion gear holding member 212 is in the normal state,the RAM 5 records size associated information in which press patterns ofthe four protrusion members 1021 provided in the first sensor 102 areassociated with the paper sizes in the width direction of the papercassette 201. In addition, when the pinion gear holding member 212undergoes lateral misalignment correction in units of 1 mm from thenormal state, the RAM 5 records size associated information in whichpress patterns of the four protrusion members 1021, which vary dependingon the amount of movement due to lateral misalignment correction, areassociated with the paper sizes.

Hereinafter, a specific example will be described. FIG. 46 is a diagramshowing a state where the four protrusion members 1021 provided in thefirst sensor 102 are pressed by the first movable member 205. As shownin FIG. 10, for convenience of explanation, the four protrusion members1021 provided in the first sensor 102 are called a protrusion a, aprotrusion b, a protrusion c, and a protrusion d when viewed from thenear side of the image forming apparatus 1.

A description will be provided for a case where the user moves thefront-side sidewall 202F and rear-side sidewall 202R in accordance witha paper size A in the normal state. The comb-teeth member 2051 of thefirst movable member 205 presses the protrusion a and the protrusion c,for example, from among the four protrusions 1021. The CPU 3 compares apress pattern of the four protrusion members 1021 of the first sensor102 with size associated information recorded in the RAM 5, in which thepress patterns are associated with the paper sizes. When the presspattern is consistent with the size associated information, the CPU 3determines that a paper of size A is stacked in the paper cassette 201.

Similarly, the user moves the front-side sidewall 202F and the rear-sidesidewall 202R in accordance with a paper size B in the normal state. Thecomb-teeth member 2051 of the first movable member 205 presses theprotrusion b and the protrusion d, for example, from among the fourprotrusion members 1021. When the press pattern is consistent with thesize associated information recorded in the RAM 5, the CPU 3 determinesthat a paper of size B is stacked in the paper cassette 201.

Here, a description will be provided for a case where the user moves thepinion gear holding member 212 by 1 mm from the normal state by lateralmisalignment correction. The user moves the front-side sidewall 202F andthe rear-side sidewall 202R in accordance with the paper size A in astate where lateral misalignment correction is made by 1 mm. At thistime, unlike the normal state, the comb-teeth member 2051 of the firstmovable member 205 presses the protrusion b and the protrusion d fromamong the four protrusion members 1021. When, the press pattern isconsistent with the size associated information recorded in the RAM 5,and thus the CPU 3 erroneously determines that a paper of size B isstacked in the paper cassette 201.

In this embodiment, the RAM 5 records the size associated information inwhich in the normal state, the press pattern of the protrusions b and dfrom among the four protrusion members 1021 is associated with the papersize B. In addition, the RAM 5 records the size associated informationin which, in a state where lateral misalignment correction is made by 1mm, the press pattern of the protrusions b and d from among the fourprotrusion members 1021 is associated with the paper size A.

If the movement distance measurement member 221 determines that thepinion gear holding member 212 undergoes lateral misalignment correctionby 1 mm, when comparing the press pattern by the first movable member205 with the size associated information, the CPU 3 acquires from theRAM 5 size associated information when lateral misalignment correctionis made by 1 mm and executes the comparison.

Similarly, the RAM 5 records size associated information in which, whenthe pinion gear holding member 212 undergoes lateral misalignmentcorrection by 2 mm from the normal state, press patterns of the fourprotrusion members 1021 are associated with the paper sizes. The same isapplied to a case where the pinion gear holding member 212 undergoeslateral misalignment correction by 3 mm or more from the normal state.

Therefore, if the movement distance measurement member 221 serving as acorrection sensor measures a movement distance of the pinion gearholding member 212 for lateral misalignment correction, when comparingthe press pattern by the first movable member 205 with size associatedinformation, the CPU 3 acquires size associated information according tothe movement distance subjected to lateral misalignment correction fromthe RAM 5 and executes the comparison.

As described above, since the RAM 5 has size associated informationaccording to the movement distance subjected to lateral misalignmentcorrection, the CPU 3 can reliably discriminate the size of a paperactually stacked in the paper cassette 201. In this example, the RAM 5records size associated information, in which press patterns of thefirst movable member 205 against the sensors of the first sensor 102 areassociated with the paper size, according to the movement distancesubjected to lateral misalignment correction, but the same is applied tothe press patterns of the second movable member 206 against the sensorsof the second sensor 103.

With the above-described configuration, lateral misalignment correctionand accurate paper size detection by the first sensor 102 can becompatibly achieved.

In the foregoing example, a plurality of protrusion members 1021 areprovided in the first sensor 102, and the comb-teeth member 2051 of thefirst movable member 205 presses the protrusion members 1021.Alternatively, instead of the protrusion members 1021, an optical sensoror a magnetic sensor may be provided. In this case, instead of thecomb-teeth member 2051, a plurality of holes or metal piecestransmitting light may be provided to the first movable member 205. Thesame is applied to the second sensor 103 or the second movable member206.

1. A paper feeding apparatus comprising: a cassette main body thatstacks a paper therein; a sidewall that moves in a width direction ofthe cassette main body; an end wall that moves in a longitudinaldirection of the cassette main body; a first movable member that rotatesaround a shaft axially fixed to the cassette main body in connectionwith the sidewall, has a first detection portion and is connected to thesidewall; a second movable member that rotates around a shaft axiallyfixed to the cassette main body in connection with the end wall, has asecond detection portion and is connected to the end wall; a firstdetection unit that detects the size of the paper in the width directionaccording to the first detection portion; a second detection unit thatdetects the size of the paper in the longitudinal direction according tothe second detection portion; a paper sensor that detects presence ofthe paper when the sidewall and the end wall are moved to positions tocome into contact with the paper and is provided on wall surfaces nearat least one of the sidewall and the end wall; and a display that, whenthe paper sensor determines paper absence, displays information that atleast one of the sidewall and the end wall is not set in accordance withthe paper size.
 2. The apparatus of claim 1, wherein, when the papersensor determines paper presence, and the size of the paper detected bythe first detection unit and the second detection unit is not consistentwith a predetermined size, the display displays that the size of thepaper is to be inputted.
 3. The apparatus of claim 2, furthercomprising: a storage unit that, when the paper size is inputted, storescombination information of a patterns detected by the first detectionunit and a patterns detected by the second detection unit for the papersize in association with the paper size; and a control unit that detectsthe paper size by comparing the patterns detected by the first detectionunit and the patterns detected by the second detection unit with thecombination information stored in the storage unit and displays resultof detecting the paper size.
 4. The apparatus of claim 3, wherein thecontrol unit controls to convey the paper by paper feed rollers when thecontrol unit detects that the paper size is correct.
 5. The apparatus ofclaim 4, wherein, when the paper sensor determines paper absence and thecontrol unit discriminates the paper size, the display displaysinformation that the size of the paper stacked in the cassette main bodyis different from the paper size based on the combination information.6. The apparatus of claim 1, wherein the paper sensor has an actuator.